A nose wheel (also called a jockey wheel) enables easy manoeuvring, coupling and uncoupling of the trailer tongue, as well as for positioning of the load. It also allows the optimum balance of the loaded trailer, which in turn reduces rolling resistance, vibrations and axle loads.
Traditionally, the nose wheel of a trailer is made of steel or cast iron with a pneumatic or solid rubber tire and metal rim. The most common type of nose wheel is the 48 mm type with a solid rubber tire. This type is commonly used for trailers for iFor Williams and are fitted with tubular main gear legs.
The nose wheel is usually mounted on the front of the trailer between the TV and the kingpin. For the best trailer aerodynamics, the V-nose should be located as close to the kingpin as possible without hitting it, which would reduce air flow resistance. For this reason, the V-nose is positioned slightly forward of the centerline of the trailer (at least at its tip). As a result, the V-nose nesehjul til tilhengere decreases the gap between TV and trailer, which reduces turbulent air flow and resulting drag on the trailer.
However, the shape of the V-nose is only a small portion of the overall trailer tow-ability equation. Other factors such as tongue distance, trailer body weight and shape, and driving speed (restrictions on 2-lane roads can often be 45 mph or lower) are more important.
The FEA model of the scaled down DMLS Ti6Al4V(ELI) nose wheel fork was constructed using a three-dimensional quadratic hexahedral solid mesh and material properties obtained experimentally as well as those of conventional aluminium alloy 7050, which were compared. Nodal strain results on the CAD model surface corresponding to the locations of the strain gauges were analysed. For the X- and Z-load cases, good correlation between the experimental and FEA results was observed.
For the X-load case, no plastic strain was experienced at the nose wheel fork. For the Z-load case, crack initiation was observed on the FEA model surface at the location of the strain gauges, which is illustrated in Fig. 11. The SEM image of the fracture surface shows partially melted powder particles at the area of crack initiation, which confirms the low-cycle fatigue behaviour presented in Table 4.
It is therefore highly recommended to use a steel or cast iron nose wheel instead of a DMLS-made one. Furthermore, it is advised to choose a design that is as close as possible to the original one, in order to achieve similar fatigue behaviour. This will guarantee the safety of both the tow vehicle and the trailer. The authors gratefully acknowledge the Centre for Rapid Prototyping and Manufacturing and Product Development Technology Station of the Central University of Free State, South Africa, for manufacturing the test jig used to mechanically test the DMLS-produced nose wheel fork. The authors are also grateful to the Department of Geology of the University of Free State for providing access to a scanning electron microscope for the microstructure evaluation of the fracture surfaces.